Nonwoven fabrics are used in absorbent articles such as sanitary products and disposable diapers, cleaning products such as wipers, and medical goods such as masks. However, the nonwoven fabrics used in such products usually have specialized functions according to the purpose of the products and their location of use.
With absorbent articles, for example, it is necessary to employ nonwoven fabrics that expand and contract in response to bodily movement during wear or use, without creating an uncomfortable feeling for the user. Disposable diapers and sanitary napkins require nonwoven fabrics with high elasticity and strength sufficient to prevent tearing during extension, as well as satisfactory feel on the skin, air permeability and liquid-permeability.
Nonwoven fabrics exhibiting the desired performance in such products are usually designed and produced for each individual product. It is therefore considered preferable, from the viewpoint of production cost and environmental protection, for nonwoven fabrics exhibiting desired performance to be more easily formed by modifying certain nonwoven fabrics such as commercially available nonwoven fabrics, and especially relatively low-cost spunbond nonwoven fabrics, meltblown nonwoven fabrics and the like.
As a method of forming a nonwoven fabric suitable for use in an absorbent article comprising a nonwoven fabric as the starting material, PTL 1 discloses a nonwoven fabric having alternating ridges and furrows each extending in one direction, with openings in the furrows, wherein the ridges have a substantially greater fiber content than the furrows, and the fiber density differs between the tops of the ridges and the edges of the openings. In paragraph [0049] of PTL 1, it is stated that an air-through nonwoven fabric or the like may be used as the starting material for the nonwoven fabric, and that it is preferred to employ a water stream or water vapor stream when using a fiber aggregate having bonds at the fiber nodes, as in an air-through nonwoven fabric.